Known constructions of retort furnaces have a chamber separating the working space from the ambient environment and ensuring achieving the required purity and quality of the process atmosphere. The retort chamber is made of heat-resisting or creep-resisting alloys and allows working temperatures up to 1300° C. The retorts have outside heat insulation and heating elements in between. The elements provide heat energy that is accumulated using the insulation and is further directed to the retort through radiation and natural convection. Heat is transferred within the retort—from its walls to the charge—in result of radiation, natural convection or convection forced using atmosphere mixers.
Usually the furnaces are equipped with systems for accelerated cooling after the heat treatment. That is achieved using blowers forcing air between the insulation and the external wall of the retort. Cold air flowing around the retort takes over the heat and heats up, then escapes outside through an open top hatch. There are also internal cooling systems operating in a closed circuit. Then, the atmosphere is drawn directly from the inside of the retort, forced through a heat exchanger and, cooled, returned to the retort.